Organisms utilize a variety of senses to judge the nature of their environment. These external cues influence internal pathways resulting in altered behavioral output and development. This application aims to elucidate thermosensory behaviors of C. elegans from gene to behavioral output, in order to better understand mechanisms of sensory signal transduction and plasticity. C. elegans senses temperature and creates a 'memory'of this temperature, which in turn dictates the navigation behavioral strategy on spatial or temporal thermal gradients. This thermal memory is plastic and can be reset upon exposure to a new temperature. In order to better understand this sensory modality and sensory plasticity in general, newly developed quantitative behavioral assays will be utilized to identify the contribution of candidate molecules, thereby outlining the underlying genetic and biochemical pathways responsible for thermosensory behavior. Calcium imaging will also be utilized in order to define where in the molecular pathway these candidate molecules function. Finally, subcellular localization of the candidate proteins will be observed in response to different temperature stimuli to gain a better understanding of where in the cell the protein acts to mediate the appropriate behavior. The combination of these approaches will provide the first comprehensive analysis of conserved molecules involved in defined aspects of thermosensation and plasticity. Multiple disorders such as retinal degeneration and inability to sense pain result from defects in sensory signaling pathways. While much is known about visual and chemosensory signal transduction in vertebrates and invertebrates, thermosensation remains poorly characterized. Exploring thermosensation in C. elegans will identify the functions of sensory molecules likely conserved in sensory signal transduction in multiple organisms. C. elegans also demonstrates long-term plasticity in its thermosensory response. Irregularities in neuronal plasticity have been linked to a number of human disorders, including drug addiction, neuronal degeneration, and epilepsy. Studying neuronal plasticity via the thermosensory behavior of C. elegans will reveal conserved molecules and mechanisms involved in nervous systems of higher order organisms.